1. Field of the Invention
The invention relates to an arrangement for deriving an electrical signal corresponding to a distance and, in particular, to an arrangement wherein a conductor loop is adapted to be arranged in a magnetic a-c field with its plane transverse to the field and a movable adjusting means is provided whose movement corresponds to the respective distance and results in adjustment of the loop.
2. Description of the Prior Art
In a typical prior art arrangement of the above type, the conductor loop is arranged in a air gap of an iron core which is excited by a winding connected to an a-c voltage source and a d-c voltage source. The dimensions of the conductor loop correspond approximately to the cross section of the iron core in the vicinity of the air gap and the loop is initially placed completely in the gap. When the conductor loop is moved so a portion of its area lies outside the gap, the magnetic flux in the iron core now passes through only the portion of the area of the loop remaining in the gap. The induced voltage at the ends of the loop, thus, becomes smaller than when the loop is totally within the gap. Through an appropriately designed electrical circuit coupled to the loop ends and, in particular, by using phase-sensitive rectification, the voltage across the loop ends can be made directly proportional to the displacement of the loop and, therefore, to a distance.
The above-described prior art arrangement is disadvantageous in that the conductor loop portion located outside the air gap of the core is not completely free of magnetic interlinkage, since it is still permeated by stray flux. The presence of this stray flux must be accounted for through the use of elaborate correction circuits when converting into a corresponding electrical signal, otherwise erroneous results will occur. If the correction circuitry is not used, then the measuring range of loop, i.e., the maximum measurable distance change, is relatively small, if a given accuracy is required. It is a further disadvantage of this prior art arrangement that the ends of the conductor loop are moved as the loop is displaced. This necessitates the use of either movable contacts or flexible wires to couple to the ends of the loop, which can have an adverse effect on the life of the arrangement.
It is an object of the present invention to provide an arrangement for obtaining an electrical signal corresponding to a distance which permits an electrical signal to be derived therefrom without the use of moving contact elements. In addition, it is a further object of the invention to provide an arrangement which permits obtaining electrical signals corresponding to large distance changes without the use of complex correction circuits.